Telephone-transmitter



(No Model.)

W. H. EOKERT.

TELEPHONE TRANSMITTER.

Patented Dec. 9, 1884.

oo'ooo INVENTOR William fl.Ec/ cert,

UNITED Sterne PATENT triers.

\VILLIAM H. EOKERT, OF NEW YORK, N. ASSIGNOR TO THE AMERICAN BELLTELEPHONE COMPANY, OF BOSTON, MASSACHUSETTS.

TELEPHONBTRANSMITTER.

SPECIFICATION forming part of Letters Patent N0. 308,956, dated December9,1884.

Application filed December 2-1, 1883.

T0 (tZZ whom it may concern.-

Be it known that I, WILLIAM H. Eonnn'r, of the city, county, and Stateof New York, a

citizen of the United States of America, have invented a new and usefulImprovement in TelephonicTransmitters, 01" which the following is aspecification.

Iam aware that others have employed for a tension-regulator, or meansfor varying the resistance in a telephonic transmitter, finely-dividedconducting material, such as finelycrushed carbon, coke, metallizedcarbon-powder, and powdered metal in a loose and free state within achamber located in close proximity to the vibrating diaphragm of themouthpiece; but in all such cases the operation of the instrument isuncertain, owing to an ab sence of capacity for maintaining adjustmentbetween contactsurfaces.

Myinvention has for its object the obtaining of a vibratory contactbetween surfaces of large area which are covered or impregnated withparticles of conducting material,whereby wide variations of electricalresistance may be effected under theinfluenceofsound-vibration,While atthe same time permanency and certainty of adjustment is attained, whichis impossible where powdered particles in a free state of movement areused. To this end I employ two sheets of metallic foil, forming bothelectrode-plates and a diaphragm, suspended side by side in contact witheach other and below themouthpieceof the transmitter. Theelectrode-plates are so bent as to form a flat surface beneath themouth-piece of the transmitter, or so as to form a \l-shaped openingbetween them. The electrode-plates, being so bent, are attached by thoseparts which are at right angles to the contact-surfaces to the supportor base-board of the mouth-piece, and the only diaphragm employed arethose parts of the electr0de-plates opposite the orifice of themouth-piece. The contact-surfaces of the foil plates are coated with anadhesive gummy substance which is impregnated with fragments orparticles of a conducting material which, when dried, forms a hard andelastic body. The material which I prefer to use for this purpose is acomposition or liquid composed ofgelatine and glycerine, gelatine bc-(No model.)

ing dissolved in water in the pro-portion of about one to five, inweight, and to this glyccriue is added to an amount of about oneeighththe weight of the gelatine. Before ap plying the paste to thecontact-surfaces of the electrode-plates a powder reduced from any goodconducting material is mixed with the paste only in sufficient quantityto .render the whole composition a conductor of high resistance. Afterbeing applied to the 'electrodeplates, and after nearly all of themoisture has been evaporated therefrom, the plates may be subjected to asufficient pressure to form the coating into a durable body.

Figure 1 isasection view of the transmitter. 6 5 Fig. 2 is a sectionview of a modified form of the electrodes. Fig. 3 is a face View of aperforated electrode.

Referring to the drawings, F and D are foil plates coated on their sideswhich are designed to face each other with a metallized paste, as abovedescribed 5 and thus prepared they are suspended, with their metallizedsurfaces facing each other and in contact with moderate pressure,beneath the orifice of the ,7 5 mouthpiece B of the transmitter.

O and E are binding-posts mounted upon a case or box, A, of thetransmitter, and said binding-posts are electrically connected to themetallized contact-plates D and F. Plates D s and F are shown in detailin Figs. 2 and 3. The electrical circuit from the battery of thetransmitter is thus completed from bindingpost 0 to contact-plate D,contact-plate F, binding-post E, and thence through the electricalcircuit and battery back to binding-post O. The contact-plates, one orboth, may be made from foil, paper, or thin sheet metal; and one only orboth of said plates may be coated with the metallized paste, as herein-0 before described.

I find that iron scalings, filings, drillings, or any finely-reducedmetal of good conducting quality is well adapted for my metallized coat-Instead of making the foil-plates into perfeet sheets, they may beperforated, leaving only a web for a body, as shown in Fig. 3. A blanksheet may be provided with interstices and then coated, leaving theinterstices filled ioo with metalliz ed material; or the plates may becoated with metallized material without filling the interstices, thusforming perforated plateelectrodes, which may in that form be attachedto and used in a telephonic transmitter.

Vibrations of the atmosphere set up in the opening B are imparted tothose parts of the electrode-plates which are exposed to the orifice,and cause an increase and decrease of pressure between the contiguoussurfaces of F and D, and a consequent change of electrical resistance inthe telephonic circuit, thereby enabling the reproduction of articulatespeech through the medium of a telephonic receiver placed at any pointin the electrical circuit.

I am aware that a teleph'one-transmitter consisting of two broad elasticelectrode-plates inclined toward each other and in contact at theirconvex ends, and constituting the electrodes, is not new; but myinvention differs from such form, in that the two plates have broadsurfaces of definite magnitude, which are in contact with each otherthroughout said surfaces, but under varying pressure, whilein thetransmitter referred to the contact is merely tangential.

I am also aware that'a comparatively rigid support for one electrode, inconnection with a broad flexible electrode which makes variable surfacecontact with the first, has been used in transmitters.

I am also aware that an electrode consisting Y of a body of carboncomposition which is subnation of two light elastic plates having broadcontiguous surfaces, forming the electrodes, said surfaces being coatedwith an inferior conductor, for the purpose specified.

2. In a contacttransmitter, the electrodes having broad surfacesnormally in contact, formed of a metallized paste, substantially asspecified.

3. A light flexible electrode, substantially as described, for acontact-transmitter havnation of two electrodes consisting of broadelastic plateswith definite extended surfaces in contact with amouthpiece arranged to concentrate the sound-waves upon the non-contacting portions of the electrodes, and to vary the pressure betweenthem.

5. In atelephone-transmitter, the combination of two electrodesconsisting of broad elastic plates having definite invariable extendedsurfaces in contact with each other.

6. In a telephone-transmitter, the combination of an electrodeconsisting of a broad elastic plate having a definite invariable extended surface adapted to make a variable electrical contact with asecond electrode of broad surface of im perfect conducting material.

V. H. EOKERT.

Witnesses:

W. B. VANSIZE, WM. ARNOUX.

